Jack beans are derived from a bulky leguminous plant also known as canavalia ensiformis, which plant is grown in tropical regions. The seed of the jack bean encased in the jack-bean hull or shell is a source of the enzyme, urease, also known as urea amidohydrolase. The enzyme, urease, derived from the jack-bean plant is commercially sold in varying forms of purity for use; for example, in home-permanent hair kits, as well as an active enzyme employed in various clinical diagnostic kits. The enzyme, urease, is sold in finepowder particulate form in accordance with specifications relating to bacterial examination and enzyme activity. Enzyme activity may be defined in one test in terms of the micromoles of ammonia liberated per minute at 25.degree. C. at a pH of 7.6 under certain confined conditions (see, for example, Sumner, J. B., Urease, Methods in Enzymology 2, p. 378 (1955), and Gorin, G. and Chin, C. C., Anal. Biochem., 17, 49-59 (1966). For example, urease might be sold with a contaminant level of ammonia of less than 0.001 micrograms per unit. Urease also is prepared and sold in connection with a specific activity of greater, for example, than 170 u/mg protein. The urease also should have a microbiological specification typically less than 1000 units per gram of nonpropagating, nonpathogenic bacteria.
The present technique of preparing urease from jack beans comprises the grinding of the seeds of the jack beans comprising the crude urease into a fine particle size, such as a ground product which has a maximum of 0.1% on a 60-mesh sieve with ethanol. Thereafter, the finely-divided jack-bean seeds are subjected to irradiation, in order to reduce the bacteria or microbiological contamination to an acceptable level, such as by irradiation of the powder through exposure to gamma radiation of a cobalt-60 source or by a Van der Graaf accelerator or some other gamma-irradiation techniques or high electron-voltage techniques. In this process, microorganisms contaminating the outer hull surface and black beans; that is, beans which are highly contaminated with bacteria or pathogens, are ground into and become part of the ground or fine-particle urease prior to irradiation. This technique raises the bacterial and pathogenic level of the material to be irradiated. By such technique, crude urease is obtained generally having an activity of greater than about 200 to 225 (mg NH.sub.3 /g sample/5 min at 25.degree. C.) and a nonpathogenic contamination of less than 1000.